django-piston-xauth/piston/utils.py

import time
from django.http import HttpResponse
from django.core.cache import cache
from django.core.mail import send_mail, mail_admins
from django.conf import settings
from django.utils.translation import ugettext as _
from django.template import loader, TemplateDoesNotExist
from django.contrib.sites.models import Site
from decorator import decorator

try:
    import json
except ImportError:
    import simplejson as json

__version__ = '0.2.3rc1-readability-branch'

def get_version():
    return __version__

# We never want to display debug information to the user about an error, but we DO want to catch and display a JSON structure when an error occurs.
# So we override this method to return a generic 500.
def format_error(error):
    json_response = dict({
        "error": True,
        "errorCode": 500,
        "message": "Readability encountered a server error. We should have been made aware of this issue automatically. If this continues, please contact us at contact@readability.com and let us know under what conditions you're receiving this error."
    })

    if settings.DEBUG:
      json_response['message'] += ' (%s)' % error
    
    return json.dumps(json_response)

class rc_factory(object):
    """
    Status codes.
    """
    CODES = dict(ALL_OK = ('OK', 200),
                 CREATED = ('Created', 201),
                 ACCEPTED = ('Accepted', 202),
                 DELETED = ('No Content', 204), # 204 says "Don't send a body!"
                 BAD_REQUEST = ('Bad Request', 400),
                 FORBIDDEN = ('Forbidden', 403),
                 NOT_FOUND = ('Not Found', 404),
                 DUPLICATE_ENTRY = ('Conflict/Duplicate', 409),
                 NOT_HERE = ('Gone', 410),
                 INTERNAL_ERROR = ('Internal Error', 500),
                 NOT_IMPLEMENTED = ('Not Implemented', 501),
                 THROTTLED = ('Throttled', 503))

    def __getattr__(self, attr):
        """
        Returns a fresh `HttpResponse` when getting 
        an "attribute". This is backwards compatible
        with 0.2, which is important.
        """
        try:
            (r, c) = self.CODES.get(attr)
        except TypeError:
            raise AttributeError(attr)

        class HttpResponseWrapper(HttpResponse):
            """
            Wrap HttpResponse and make sure that the internal _is_string 
            flag is updated when the _set_content method (via the content 
            property) is called
            """
            def _set_content(self, content):
                """
                Set the _container and _is_string properties based on the 
                type of the value parameter. This logic is in the construtor
                for HttpResponse, but doesn't get repeated when setting 
                HttpResponse.content although this bug report (feature request)
                suggests that it should: http://code.djangoproject.com/ticket/9403 
                """
                if not isinstance(content, basestring) and hasattr(content, '__iter__'):
                    self._container = content
                    self._is_string = False
                else:
                    self._container = [content]
                    self._is_string = True

            content = property(HttpResponse._get_content, _set_content)            

        return HttpResponseWrapper(r, content_type='text/plain', status=c)
    
rc = rc_factory()
    
class FormValidationError(Exception):
    def __init__(self, form):
        self.form = form

class HttpStatusCode(Exception):
    def __init__(self, response):
        self.response = response

def validate(v_form, operation='POST'):
    @decorator
    def wrap(f, self, request, *a, **kwa):
        form = v_form(getattr(request, operation))
    
        if form.is_valid():
            setattr(request, 'form', form)
            return f(self, request, *a, **kwa)
        else:
            raise FormValidationError(form)
    return wrap

def throttle(max_requests, timeout=60*60, extra=''):
    """
    Simple throttling decorator, caches
    the amount of requests made in cache.
    
    If used on a view where users are required to
    log in, the username is used, otherwise the
    IP address of the originating request is used.
    
    Parameters::
     - `max_requests`: The maximum number of requests
     - `timeout`: The timeout for the cache entry (default: 1 hour)
    """
    @decorator
    def wrap(f, self, request, *args, **kwargs):
        if request.user.is_authenticated():
            ident = request.user.username
        else:
            ident = request.META.get('REMOTE_ADDR', None)
    
        if hasattr(request, 'throttle_extra'):
            """
            Since we want to be able to throttle on a per-
            application basis, it's important that we realize
            that `throttle_extra` might be set on the request
            object. If so, append the identifier name with it.
            """
            ident += ':%s' % str(request.throttle_extra)
        
        if ident:
            """
            Preferrably we'd use incr/decr here, since they're
            atomic in memcached, but it's in django-trunk so we
            can't use it yet. If someone sees this after it's in
            stable, you can change it here.
            """
            ident += ':%s' % extra
    
            now = time.time()
            count, expiration = cache.get(ident, (1, None))

            if expiration is None:
                expiration = now + timeout

            if count >= max_requests and expiration > now:
                t = rc.THROTTLED
                wait = int(expiration - now)
                t.content = 'Throttled, wait %d seconds.' % wait
                t['Retry-After'] = wait
                return t

            cache.set(ident, (count+1, expiration), (expiration - now))
    
        return f(self, request, *args, **kwargs)
    return wrap

def coerce_put_post(request):
    """
    Django doesn't particularly understand REST.
    In case we send data over PUT, Django won't
    actually look at the data and load it. We need
    to twist its arm here.
    
    The try/except abominiation here is due to a bug
    in mod_python. This should fix it.
    """
    if request.method == "PUT":
        # Bug fix: if _load_post_and_files has already been called, for
        # example by middleware accessing request.POST, the below code to
        # pretend the request is a POST instead of a PUT will be too late
        # to make a difference. Also calling _load_post_and_files will result 
        # in the following exception:
        #   AttributeError: You cannot set the upload handlers after the upload has been processed.
        # The fix is to check for the presence of the _post field which is set 
        # the first time _load_post_and_files is called (both by wsgi.py and 
        # modpython.py). If it's set, the request has to be 'reset' to redo
        # the query value parsing in POST mode.
        if hasattr(request, '_post'):
            del request._post
            del request._files
        
        try:
            request.method = "POST"
            request._load_post_and_files()
            request.method = "PUT"
        except AttributeError:
            request.META['REQUEST_METHOD'] = 'POST'
            request._load_post_and_files()
            request.META['REQUEST_METHOD'] = 'PUT'
            
        request.PUT = request.POST


class MimerDataException(Exception):
    """
    Raised if the content_type and data don't match
    """
    pass

class Mimer(object):
    TYPES = dict()
    
    def __init__(self, request):
        self.request = request
        
    def is_multipart(self):
        content_type = self.content_type()

        if content_type is not None:
            return content_type.lstrip().startswith('multipart')

        return False

    def loader_for_type(self, ctype):
        """
        Gets a function ref to deserialize content
        for a certain mimetype.
        """
        for loadee, mimes in Mimer.TYPES.iteritems():
            for mime in mimes:
                if ctype.startswith(mime):
                    return loadee
                    
    def content_type(self):
        """
        Returns the content type of the request in all cases where it is
        different than a submitted form - application/x-www-form-urlencoded
        """
        type_formencoded = "application/x-www-form-urlencoded"

        ctype = self.request.META.get('CONTENT_TYPE', type_formencoded)
        
        if type_formencoded in ctype:
            return None
        
        return ctype

    def translate(self):
        """
        Will look at the `Content-type` sent by the client, and maybe
        deserialize the contents into the format they sent. This will
        work for JSON, YAML, XML and Pickle. Since the data is not just
        key-value (and maybe just a list), the data will be placed on
        `request.data` instead, and the handler will have to read from
        there.
        
        It will also set `request.content_type` so the handler has an easy
        way to tell what's going on. `request.content_type` will always be
        None for form-encoded and/or multipart form data (what your browser sends.)
        """    
        ctype = self.content_type()
        self.request.content_type = ctype
        
        if not self.is_multipart() and ctype:
            loadee = self.loader_for_type(ctype)
            
            if loadee:
                try:
                    self.request.data = loadee(self.request.raw_post_data)
                        
                    # Reset both POST and PUT from request, as its
                    # misleading having their presence around.
                    self.request.POST = self.request.PUT = dict()
                except (TypeError, ValueError):
                    # This also catches if loadee is None.
                    raise MimerDataException
            else:
                self.request.data = None

        return self.request
                
    @classmethod
    def register(cls, loadee, types):
        cls.TYPES[loadee] = types
        
    @classmethod
    def unregister(cls, loadee):
        return cls.TYPES.pop(loadee)

def translate_mime(request):
    request = Mimer(request).translate()
    
def require_mime(*mimes):
    """
    Decorator requiring a certain mimetype. There's a nifty
    helper called `require_extended` below which requires everything
    we support except for post-data via form.
    """
    @decorator
    def wrap(f, self, request, *args, **kwargs):
        m = Mimer(request)
        realmimes = set()

        rewrite = { 'json':   'application/json',
                    'yaml':   'application/x-yaml',
                    'xml':    'text/xml',
                    'pickle': 'application/python-pickle' }

        for idx, mime in enumerate(mimes):
            realmimes.add(rewrite.get(mime, mime))

        if not m.content_type() in realmimes:
            return rc.BAD_REQUEST

        return f(self, request, *args, **kwargs)
    return wrap

require_extended = require_mime('json', 'yaml', 'xml', 'pickle')
    
def send_consumer_mail(consumer):
    """
    Send a consumer an email depending on what their status is.
    """
    try:
        subject = settings.PISTON_OAUTH_EMAIL_SUBJECTS[consumer.status]
    except AttributeError:
        subject = "Your API Consumer for %s " % Site.objects.get_current().name
        if consumer.status == "accepted":
            subject += "was accepted!"
        elif consumer.status == "canceled":
            subject += "has been canceled."
        elif consumer.status == "rejected":
            subject += "has been rejected."
        else: 
            subject += "is awaiting approval."

    template = "piston/mails/consumer_%s.txt" % consumer.status    
    
    try:
        body = loader.render_to_string(template, 
            { 'consumer' : consumer, 'user' : consumer.user })
    except TemplateDoesNotExist:
        """ 
        They haven't set up the templates, which means they might not want
        these emails sent.
        """
        return 

    try:
        sender = settings.PISTON_FROM_EMAIL
    except AttributeError:
        sender = settings.DEFAULT_FROM_EMAIL

    if consumer.user:
        send_mail(_(subject), body, sender, [consumer.user.email], fail_silently=True)

    if consumer.status == 'pending' and len(settings.ADMINS):
        mail_admins(_(subject), body, fail_silently=True)

    if settings.DEBUG and consumer.user:
        print "Mail being sent, to=%s" % consumer.user.email
        print "Subject: %s" % _(subject)
        print body

def head_guard(f):
    """
    Decorator to make sure that responses to HEAD requests have empty
    body.
    """

    def wrap(self, request, *args, **kwargs):
        response = f(self, request, *args, **kwargs)
        if request.method == "HEAD":
            response.content = ''
        return response
    return wrap